The proposed conference will be the ninth in a series of Gordon Conferences on Lysosomes, which are held regularly on alternate years. They bring together leading investigators in cell biology, infectious and metabolic diseases, immunology, pathology, and physiology. The 1980 conference will emphasize basic problems in mammalian biology and pathology and will bring together active investigators in a number of areas dealing with the role of lysosomes in uptake, transport, storage, and recycling of membrane and membrane-bound macromolecules. A new concept of the function of lysosomes has been emerging over the last few years. It is becoming apparent that the lysosomal system is not just the garbage dump where cell debris is scavenged and sorted over--some degraded and recycled, some sequestered forever. Rather, through the process of selective endocytosis, many biologically active substances, such as hormones, enzymes, LDL, antibodies, and toxins are internalized, and may, or may not, be degraded within lysosomes. The fate of the substance which binds to the receptor, the synthesis and fate of the receptor, and the manner by which binding and internalization of either or both bound substance and receptor initiate a chain of events leading to an appropriate biologic response are central issues now in endocrinology, neurology, and cell biology. The role of the lysosomal system in these events may therefore be central to understanding and controlling the effects of these exogenous products on the target cells which ultimately carry out specific functions. Since work in this broad field does not conform to established disciplines in biology and medicine, the Gordon Conference on Lysosomes is an extremely valuable mechanism for communication and discussion among investigators. Several of the topics will deal with very recent advances which have not been extensively covered at similar meetings. For this reason a setting such that traditional with the Gordon Conferences, which favors free and informal exchange of new findings and ideas, will be particularly advantageous.